Method of producing a metallic carrier systems for supporting semi-conductor elements have heretofore comprised an outer frame with individual feed lines extending tongue-like toward the center of the frame, and in the band plane. One of these tongue-like feed lines has served as a carrier for the semi-conductor chip and is attached thereto by means of welding or soldering or gluing. The other feed lines extend ahead of the semi-conductor chip and are conductively connected with the associated electrodes of the semi-conductor chip by fine wires. The entire assembly is then frequently imbedded in a plastic, ceramic or glass housing. While such a carrier system has been satisfactory, the connections from the ends of the feed lines to the semi-conductor chip must be done by hand, usually through the help of a microscope or strong glass, and are very laborious and tedious operations.
Another method of mounting and contacting the semi-conductor chip is described in the German Offenlegengesschrift 1,930,627 in which one or several monolithic semi-conductor components are applied onto a carrier plate provided with conductor paths in the form of a thin-film circuit. The conductor paths at the connection points are welded to the connection paths of the semi-conductor components, with the connection extending to the outside and produced by means of etching from a copper lined aluminum sheet. Such a contacting means makes it unnecessary to solder the connection wires, but is relatively complicated and expensive to manufacture.
A further method for supporting and providing contact with a semi-conductor member having a plurality of electrodes has consisted in a system of electric feed lines, produced from metal sheet, which extend tongue-like from a mounting frame into the interior of the frame and are conductively connected with the individual electrodes of the semi-conductor member. This metallic carrier system may be made by punching or etching, but is difficult to manufacture and particularly to produce the fine structure of the feed lines and the coarse structure of the connecting legs in one piece, and requires extremely careful workmanship.
The present invention provides a metallic carrier system for mounting and contacting a semi-conductor chip and method of producing the same, which can be produced in a simple and expeditious manner.
In carrying out the invention, the simplicity in production of the carrier system is attained by using a comparatively inexpensive metal for the relatively thick support and connection legs and a different metal, which may readily be connected to the electrodes of a semi-conductor chip for the relatively thin inner feed lines, to facilitate the connection of the inner feed lines to the electrodes of a semi-conductor chip.
It is particularly advantageous to make the outer connection legs from brass and the inner feed lines from nickel and to so form the inner feed lines as to have uniformly curved expansion sections intermediate their ends curving out of the planes of the feed lines, to provide an accordian effect and increase the yieldability of the feed lines and equalize thermic expansion between the semi-conductor substrate and the coarse structure of the connection legs of the carrier system.
As a further advantage of the invention, the metallic carrier system may be produced by etching from a multi-layer material, the layers of which may be of different etching resistance to selectively etch the inner feed lines and the outer connection legs through the application of etching masks.
A further advantage of the invention is to provide two different etching agents, one for etching the inner feed lines and the other for etching the outer connection legs, in which the fine structure of the inner feed lines may be etched slower than the coarse structure of the connection legs, in comparison with the thickness ratio between the inner feed lines and the outer connection legs.
In the etching process, a covering mask may be produced on a carrier sheet by a photo-lithographic process and produce the inner feed lines by galvanic deposition of the metal, while not affecting the metal of the carrier sheet, and then removing the covering mask and covering the fine structure of the feed lines with a protective lacquer and etching mask, for the production of the outer connection legs by selective etching.
It is also of advantage to recess the carrier sheet in the regions of the paths of the inner feed lines to produce curved expansible sections in the inner feed lines as galvanically deposited thereon, to attain the desired shape and yieldability of the inner feed lines.
A further advantage of the invention is that is possible to deposit galvanically two layers of different metals, for example copper and nickel, which form together the inner feed lines. The layer directly connected with the electrodes of the semi-conductor-chip can then be made very thin.
Other objects, features and advantages of the invention will be readily apparent from the following description of certain preferred embodiments thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure.